1. Field of the Invention
The present invention relates to an apparatus for jetting ink of an ink-jet print head, and more particularly, to an apparatus for jetting ink by utilizing a magnetic force.
2. Description of the Prior Art
Apparatuses for jetting ink applied to conventional drop-on-demand (DOD) ink-jet print heads employ either a heating system which uses a surface heating element or a piezoelectric system which uses a piezoelectric element.
As shown in FIG. 1, an apparatus 10 for jetting ink of the heating system is formed such that a lower insulating layer 14, a heating element 16, electrodes 18, an upper insulating layer 20 and a protecting layer 22 are sequentially stacked on a printed circuit board (hereinafter referred to as "PCB") 12. Passage walls 23 are installed between a nozzle plate 24 and the protecting layer 22 to form an ink chamber 26. Then, the ink chamber 26 is connected to a reservoir (not shown), and both electrodes 18 are connected with a driving signal generator 28.
When a driving signal is supplied to the electrodes 18 from the driving signal generator 28, heating element 16 is heated, and ink 27 within the ink chamber 26 is boiled. At this time, bubbles 29 are produced within the ink chamber 26, and the bubbles 29 push the ink 27 within the ink chamber 26 out of a nozzle 25 of the nozzle plate 24, thereby ejecting an ink jet 30. The ink jet 30 is ejected from the nozzle 25 in accordance with the driving signal, i.e., a print signal.
As shown in FIG. 2, an apparatus 40 for jetting ink of a piezoelectric system is provided with a PCB 42, a diaphragm 44, a piezoelectric element 46, a spacer 48 and a nozzle plate 50. An ink chamber 54 is formed by the diaphragm 44, the piezoelectric element 46 and the nozzle plate 50. The interior of the ink chamber 54 is filled with ink 53.
If a driving signal is supplied to the piezoelectric element 46 from a driving signal generator 52, the piezoelectric element 46 mechanically expands and contracts. An ink jet 55 is produced by ejecting the ink 53 within the ink chamber 54 out of the nozzle 51 by the expanding and contracting action of the piezoelectric element 46.
However, the apparatus 10 for jetting ink using the heating system deleteriously requires so much time for generating the bubbles that the ejecting speed of the ink, i.e., the print speed, is slowed down, and the characteristics of the heat emitting body (heating element 16) are liable to be changed in connection with the surrounding temperature. The apparatus 40 for jetting ink using the piezoelectric system has a drawback of incurring high cost due to the use of the high-priced piezoelectric element 46.
Furthermore, both ink-jet apparatuses 10 and 40, using the heating system and the piezoelectric system, respectively, involve a fastidious manufacturing process which thereby degrades the productivity of such apparatuses.
On the other hand, U.S. Pat. Nos. 4,057,807 and 4,210,920 disclose ink-jet apparatuses for ejecting ink by vibrating a magnetically active diaphragm plate by means of an electromagnet.
The ink-jet apparatuses described in the above U.S. Pat. Nos. 4,057,807 and 4,210,920 are equipped with a magnet driver attached to the outside of a nozzle of a head and the magnetically active diaphragm plate for sealing an ink chamber. The ink is ejected by a pressure which is exerted when the magnetically active diaphragm plate is deformed by a magnetic field generated by the magnet driver.
However, according to these conventional ink-jet apparatuses, when any one magnet driver coil is magnetized, a secondary current becomes induced to another driver coil nearby. Therefore, the magnetically active diaphragm plate of another magnet driver side is activated to eject the ink from another undesired nozzle.
Therefore, it is difficult to obtain a favorable printing quality. Further, the magnet driver is attached to the outside of the nozzle to make the ink-jet apparatus bulky in its construction.